U.S. patent application number 10/802731 was filed with the patent office on 2005-03-10 for power circuit of a vehicular electronic control unit.
This patent application is currently assigned to MITSUBISHI DENKI KABUSHIKI KAISHA. Invention is credited to Sayama, Masahiko.
Application Number | 20050052081 10/802731 |
Document ID | / |
Family ID | 34225162 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050052081 |
Kind Code |
A1 |
Sayama, Masahiko |
March 10, 2005 |
Power circuit of a vehicular electronic control unit
Abstract
A power circuit of a vehicular electronic control unit is
provided with a constant voltage power circuit, an awakening timer
circuit, and first and second power supply circuits each of which
is supplied with power from a vehicle battery. The constant voltage
power circuit is supplied with power from the vehicle battery via
the first and second power supply circuits. The awakening timer
circuit generates an awakening trigger signal upon a lapse of a
prescribed time from a stop of power supply to the microprocessor.
The first power supply circuit has an output contact as a first
opening/closing element and a coil for closing the output contact.
The second power supply circuit has a second opening/closing
element that is provided between the vehicle battery and the
constant voltage power circuit and is closed at least in response
to the awakening trigger signal.
Inventors: |
Sayama, Masahiko; (Hyogo,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
MITSUBISHI DENKI KABUSHIKI
KAISHA
|
Family ID: |
34225162 |
Appl. No.: |
10/802731 |
Filed: |
March 18, 2004 |
Current U.S.
Class: |
307/10.1 |
Current CPC
Class: |
B60R 16/03 20130101;
H02J 2310/46 20200101; H02J 1/14 20130101 |
Class at
Publication: |
307/010.1 |
International
Class: |
B60L 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2003 |
JP |
P2003-314223 |
Claims
What is claimed is:
1. A power circuit of a vehicular electronic control unit including
a microprocessor for driving various electric loads in accordance
with operation states of various input sensors and contents of a
program memory, the power circuit comprising a constant voltage
power circuit, an awakening timer circuit, and first and second
power supply circuits each of which is supplied with power from a
vehicle battery, wherein: the constant voltage power circuit is
supplied with power from the vehicle battery via the first or
second power supply circuit; the awakening timer circuit generates
an awakening trigger signal upon a lapse of a prescribed time from
a stop of power supply to the microprocessor; the first power
supply circuit comprises an output contact as a first
opening/closing element and a coil for closing the output contact;
and the second power supply circuit comprises a second
opening/closing element that is provided between the vehicle
battery and the constant voltage power circuit and is closed in
response to the awakening trigger signal.
2. A power circuit of a vehicular electronic control unit including
a microprocessor that is supplied with power from a vehicle battery
and drives various electric loads in accordance with operation
states of various input sensors and contents of a program memory,
the power circuit comprising: a constant voltage power circuit that
is supplied with power from the vehicle battery via the first or
second power supply circuit, and that supplies a prescribed
regulated voltage to the microprocessor, devices accompanying the
microprocessor including the program memory and a RAM for
computation, and input/output interface circuits; an awakening
timer circuit that is supplied with power directly from the vehicle
battery, and generates an awakening trigger signal upon a lapse of
a prescribed time from a stop of power supply to the
microprocessor; a first power supply circuit that comprises a power
relay having an output contact as a first opening/closing element
provided between the vehicle battery and the constant voltage power
circuit or between and the vehicle battery and the various electric
loads, and a coil for closing the output contact, and a
reverse-blocking diode connected in series to the output contact,
wherein the coil being energized when a power switch is turned on
and kept energized by a power maintenance drive signal generated by
the microprocessor even if the power switch is turned off; and a
second power supply circuit comprises a second opening/closing
element that connects the vehicle battery and the constant voltage
power circuit, and is closed in response to the awakening trigger
signal and kept closed by a power maintenance drive signal
generated by the microprocessor, wherein the reverse-blocking diode
is in such a connection relationship as to allow power supply from
the first power supply circuit to the various electric loads and to
prohibit power supply from the second power supply circuit to the
various electric loads.
3. The power circuit of a vehicular electronic control unit
according to claim 1, wherein the vehicular electronic control unit
is housed in a case, the power relay is disposed outside the case,
and the second opening/closing element is a transistor that is
disposed inside the case.
4. A power circuit of a vehicular electronic control unit
comprising a microprocessor that is supplied with power from a
vehicle battery and drives various electric loads in accordance
with operation states of various input sensors and contents of a
program memory, the power circuit comprising: a constant voltage
power circuit that is supplied with power from the vehicle battery
via the first or second power supply circuit, and that supplies a
prescribed regulated voltage to the microprocessor, devices
accompanying the microprocessor including the program memory and a
RAM for computation, and input/output interface circuits; an
awakening timer circuit that is supplied with power directly from
the vehicle battery, and generates an awakening trigger signal upon
a lapse of a prescribed time from a stop of power supply to the
microprocessor; a first power supply circuit that comprises a power
relay having an output contact as a first opening/closing element
provided between the vehicle battery and the constant voltage power
circuit or between and the vehicle battery and the various electric
loads, and a coil for closing the output contact, and a
reverse-blocking diode connected in series to the output contact,
wherein the coil being energized when a power switch that is
manipulated to start driving of a vehicle is turned on and kept
energized by a power maintenance drive signal generated by the
microprocessor even if the power switch is turned off; and a second
power supply circuit comprises a second power relay having an
output contact as a second opening/closing element provided between
the vehicle battery and the constant voltage power circuit, and a
coil for closing the output contact, wherein the coil being
energized in response to the awakening trigger signal and kept
energized by a power maintenance drive signal generated by the
microprocessor, wherein the reverse-blocking diode is in such a
connection relationship as to allow power supply from the first
power supply circuit to the various electric loads and to prohibit
power supply from the second power supply circuit to the various
electric loads.
5. The power circuit of a vehicular electronic control unit
according to claim 1, wherein first and second power control
signals are input to the microprocessor, a program as power
maintaining means is stored in the program memory, the first power
control signal are an opening/closing signal of the power switch,
and the second power control signal is the awakening trigger signal
generated by the awakening timer circuit, and wherein the power
maintaining means generates, when the power switch is opened, a
power maintenance drive signal for keeping power supply through the
first power supply circuit during a first period that is necessary
for save control processing of the microprocessor, and while the
power switch is off, the power maintaining means generates a power
maintenance drive signal for keeping power supply through the
second power supply circuit during a second period for monitoring
of a state of a particular input signal.
6. The power circuit of a vehicular electronic control unit
according to claim 5, wherein a timer operation start instruction
signal is input from the microcomputer to the awakening timer
circuit and a program as awakening control means is stored in the
program memory, and wherein the awakening control means causes a
next awakening operation by causing generation of the timer
operation start instruction signal immediately before a stop of
generation of the power maintenance drive signal, and prohibits a
subsequent awakening operation by stopping generation of the timer
operation start instruction signal in accordance with a monitoring
result of the particular input signal.
7. The power circuit of a vehicular electronic control unit
according to claim 5, wherein the power maintenance drive signal is
output to the first and second power supply circuits from a common
output port of the microprocessor and the power circuit further
comprises an AND circuit and an OR circuit, and wherein the AND
circuit generates a first logical signal when the output contact as
the first opening/closing element is closed and the power
maintenance drive signal is generated, the OR circuit calculates OR
of the first logical signal and a second logical signal that is
generated when the power switch is closed, and the coil of the
power relay is energized by a resulting OR signal of the OR
circuit.
8. The power circuit of a vehicular electronic control unit
according to claim 4, wherein the various input sensors are
separately connected to the microprocessor through first and second
input interface circuits, wherein first-group input sensors that
are connected to the first input interface circuit are also
connected to the first power supply circuit and are a group of
sensors that need not be monitored while the power switch is off,
and wherein second-group input sensors that are connected to the
second input interface circuit are also connected to the second
power supply circuit and are a group of sensors that need to be
monitored while the power switch is off or a group of sensors whose
current consumption is very small though they need not be monitored
while the power switch is off.
9. The power circuit of a vehicular electronic control unit
according to claim 4, wherein a program as alarming/displaying
means is stored in the program memory, and wherein the
alarming/displaying means causes an abnormality storage circuit to
operate and thereby announces occurrence of an abnormality using an
alarm/display if the output contact as the first opening/closing
element is closed in a state that the power switch is off and the
power maintenance drive signal is not generated.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a power circuit of a
vehicular electronic control unit incorporating a microprocessor
for performing, for example, an ignition control and a fuel
injection control on a vehicle engine. In particular, the invention
relates to improvement of a power circuit for supplying control
power to a vehicular electronic control unit exceptionally in spite
of a power switch's being in an off-state.
[0003] 2. Description of the Related Art
[0004] A technique of using both of a sleep power circuit and a
control power circuit as power circuits of a vehicular electronic
control unit are widely put in practical use. The sleep power
circuit directly connects a vehicle battery to the vehicular
electronic control unit to maintain data stored in a RAM that
cooperates with a microprocessor that is incorporated in the
vehicular electronic control unit. The control power circuit
connects the vehicle battery to the vehicular electronic control
unit at the output contact of an electromagnetic relay having a
coil that is energized by the vehicle battery via a power
switch.
[0005] Once activated, the electromagnetic relay is supplied with
an operation maintenance signal from the microprocessor and
continues its relaying state until the microprocessor completes
various save controls even if the power switch is turned off. This
kind of power supply state is called sleep power supply.
[0006] As exemplified above, many methods for continuing supply of
power for a prescribed time after turning-off of a power switch
have been proposed. For example, Japanese patent application
JP-A-5-18315 (assigned to the same assignee of this application)
discloses a concept that power shutoff of a vehicular electronic
control unit (ECU) is delayed to allow recovery, to an initial
position, of a stepping motor that is one of vehicle electric
loads. The delay of power shutoff secures a time to transfer part
of learned information stored in a RAM to a nonvolatile memory such
as an EEPROM and make it stored there.
[0007] Another prior art technique for supplying control power to a
vehicular electronic control unit though a power switch is in an
off-state is disclosed in Japanese patent application
JP-A-2003-74421 (assigned to DENSO CORP). That is, JP-A-2003-74421
discloses what is called a regular activation concept that a
vehicular computer is supplied with power every predetermined time
after a stop of the engine, whereby the states of particular
sensors such as a fuel tank internal pressure sensor, a remaining
fuel sensor, and a tank internal temperature sensor are monitored
and occurrence/non-occurrence of fuel leakage or transpiration is
judged.
[0008] In the techniques of JP-A-5-18315 and patent
JP-A-2003-74421, the delayed power shutoff or the regular
activation is performed individually, that is, the power circuit is
not configured so that both of the delayed power shutoff and the
regular activation can be performed in parallel. The technique of
JP-A-5-18315 has a problem that if the microprocessor is activated
regularly while the power switch is off, unnecessary power supply
to various vehicle electric loads occurs to increase the
consumption of current supplied from the vehicle battery.
[0009] In the power circuit of JP-A-2003-74421, vehicle electric
loads are supplied with power directly from the power switch.
Therefore, the power switch needs to deal with a large current and
the delayed power shutoff cannot be performed.
SUMMARY OF THE INVENTION
[0010] A first object of the present invention is therefore to
provide a safe power circuit that makes control power for a
vehicular electronic control unit effective while a power switch is
off and that has functions of delayed power shutoff and regular
activation.
[0011] A second object of the invention is to provide a power
circuit that supplies performs power supply to vehicle electric
loads and power supply to a vehicular electronic control unit in a
unified manner while the vehicle is driven and that prevents an
event that power is supplied to only one of the vehicular
electronic control unit and the vehicle electric loads at the
occurrence of an abnormality.
[0012] To attain the above objects, the invention provides a power
circuit of a vehicular electronic control unit having a
microprocessor that is supplied with power from a vehicle battery
and that drives various electric loads in accordance with the
operation states of various input sensors that generate an on/off
signal or an analog signal and the contents of a program memory.
The vehicular electronic control unit is provided with a constant
voltage power circuit, an awakening timer circuit, and first and
second power supply circuits.
[0013] The constant voltage power circuit is supplied with power
from the vehicle battery via the first or second power supply
circuit, and supplies a prescribed regulated voltage to the
microprocessor, the devices accompanying the microprocessor such as
a program memory and a RAM for computation, and input/output
interface circuits.
[0014] The awakening timer circuit is supplied with power directly
from the vehicle battery and generates an awakening trigger signal
upon a lapse of a prescribed time from a stop of power supply to
the microprocessor. The awakening timer circuit employs
power-saving-type circuit elements.
[0015] The first power supply circuit is provided with a power
relay having an output contact as a first opening/closing element
provided between the vehicle battery and the constant voltage power
circuit/various electric loads and a coil for closing the output
contact, and a reverse-blocking diode that is connected in series
to the output contact. The coil is energized when the power switch
is closed, that is, manipulated at a start of driving of the
vehicle. Even if the power switch is opened, the coil is kept
energized by a power maintenance drive signal that is generated by
the microprocessor.
[0016] The second power supply circuit is provided with a second
opening/closing element that at least connects the vehicle battery
and the constant voltage power circuit. The second opening/closing
element is closed when an awakening trigger signal is generated,
and is kept closed by a power maintenance drive signal that is
generated by the microprocessor.
[0017] The reverse-blocking diode is in such a connection
relationship as to allow power supply from the first power supply
circuit to the various electric loads and to prohibit power supply
from the second power supply circuit to the various electric
loads.
[0018] Therefore, during a driving operation of the vehicular
electronic control unit, the vehicular electronic control unit and
the vehicle electric loads are supplied with power from the single
power relay rather than separate power supply circuits. That is,
the power circuit is not configured so as to supply power to one of
the vehicular electronic control unit and the vehicle electric
loads from the power relay when an abnormality occurs in the power
circuit. Further, when the vehicular electronic control unit is
activated in a state that the power switch is off, the vehicle
electric loads are not supplied with power.
[0019] In the power circuit of a vehicular electronic control
apparatus according to the invention, during a driving operation of
the vehicular electronic control unit, the vehicular electronic
control unit and the vehicle electric loads are supplied with power
from the single power relay rather than separate power supply
circuits. Therefore, when a contact failure, a welding abnormality,
or the like has occurred in the power relay, it is not necessary to
perform complex processing. The driver can easily recognize and
deal with such a contact failure or welding abnormality.
[0020] When the vehicular electronic control unit is activated by
an awakening operation in a state that the driver is absent and the
power switch is off, the vehicle electric loads are not supplied
with power. Therefore, the consumption of power that is supplied
from the vehicle battery can be reduced and a burning damage
accident caused by occurrence of an abnormality can be
prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a circuit diagram showing the configuration of the
entire power circuit of a vehicular electronic control unit
according to a first embodiment of the invention; and
[0022] FIG. 2 is a circuit diagram showing the configuration of the
entire power circuit of a vehicular electronic control unit
according to a second embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Embodiment 1
[0024] FIG. 1 is a circuit diagram showing the configuration of the
entire power circuit of a vehicular electronic control unit
according to a first embodiment of the invention. The configuration
of the power circuit will be described below in detail.
[0025] In FIG. 1, reference symbol 100a denotes a vehicular
electronic control unit that is housed in a tightly closed case and
connected to external devices described below.
[0026] Reference symbol 101 denotes a DC 12 V system vehicle
battery; 102, a power switch such as an ignition switch that is
manipulated when driving of the vehicle is started or stopped; 104,
a power relay having an output contact 104a and a coil 104b; 105,
various input sensors that perform on/off operations such as an
engine rotation sensor, a crank angle sensor, a vehicle speed
sensor, and a shift switch for detecting a shift lever position of
the transmission; 107, various analog input sensors such as an
accelerator position sensor for detecting a degree of pedaling on
the accelerator, a throttle position sensor for detecting a degree
of opening of a throttle valve, an air flow sensor that is attached
to an intake pipe, an exhaust gas sensor, a fuel tank temperature
sensor, remaining fuel sensor, and pressure sensor, a cooling water
sensor, and a cylinder pressure sensor; and 108a and 109a, many
vehicle electric loads such as an energization coil of a stepping
motor. Other vehicle electric loads include ignition coils and a
fuel injection electromagnetic valve throttle control motor.
[0027] Next, the internal configuration of the vehicular electronic
control unit 100a will be described. Reference symbol 110a denotes
a microprocessor; 111a, a program memory such as a flash memory
that is bus-connected to the microprocessor 110a; 112a, a control
program as a power maintaining means (described later) that is
stored in the program memory 111a; 113a, a control program as an
awakening control means (described later) that is stored in the
program memory 111a; 114, a RAM for computation that is
bus-connected to the microprocessor 110a; and 115, a nonvolatile
data memory such as an EEPROM that is serially connected to the
microprocessor 110a and on which reading and writing can be
performed electrically.
[0028] Reference numeral 120 denotes an awakening timer circuit
using low-power-consumption field-effect transistors as used in
calendar clocks. Supplied with power directly from the vehicle
battery 101, the awakening timer circuit 120 starts a timer
operation upon instantaneously receiving a timer operation start
instruction signal Dy2 that is generated by the microprocessor
110a. Upon a lapse of a preset, prescribed time, the awakening
timer circuit 120 generates an awakening trigger signal Awk, which
is supplied to an input of an OR element 145 (described later) and
is also supplied to a second input circuit 121, which, in response,
supplies a second power control signal Dx2 to the microprocessor
110a.
[0029] Reference numeral 130 denotes a memory retention power
circuit that is supplied with power directly from the vehicle
battery 101. Incorporating a high-resistance input resistor and a
constant voltage control circuit (not shown), the memory retention
power circuit 130 serves as a low-power-consumption power source
for supplying a retention voltage Vsp to be used for maintaining
the storage contents of the RAM 114 even while a circuit (described
later) for supplying power to the vehicular electronic control unit
100a is off. Reference numeral 140 denotes a constant voltage power
circuit for supplying main power. The constant voltage power
circuit 140 is supplied with power from the vehicle battery 101 via
the output contact 104a as a first opening/closing element and a
reverse-blocking diode 141, and generates a constant voltage Vcc of
DC 5 V, for example.
[0030] The constant voltage power circuit 140 supplies a prescribed
regulated voltage to the microprocessor 110a, the devices
accompanying the microprocessor 110a such as the program memory
111a, the RAM 114 for computation, and the nonvolatile data memory
115, and input/output interface circuits 150, 170, and 180a
(described later).
[0031] Reference numeral 150 denotes the input interface circuit
that is provided between the various input sensors 105 that perform
on/off operations and a digital input port Dx0 of the
microprocessor 110a. Reference numeral 151 denotes a bleeder
resistor that is provided between the connecting point of the
output contact 104a and the reverse-blocking diode 141 and the
various input sensors 105. The input interface circuit 150
level-converts DC 12 V as an input signal voltage into DC 5 V and
incorporates a capacitor as a noise filter.
[0032] It is intended that a relatively large current flows through
the bleeder resistor 151 to prevent a contact failure at the
contact by causing a flow of a sufficiently large contact current
when an input sensor 105 is closed, and to suppress noise occurring
on the signal lines even in the case where the input sensors 105
are transistor switches. When an input sensor 105 is opened, the
bleeder resistor 151 pulls up its voltage to the positive side
(i.e., to the voltage of the vehicle battery 101).
[0033] Reference numeral 152 denotes an OR circuit that receives,
as inputs, a first logical signal that is an output of an AND
circuit 155 (described later) and a second logical signal that is
an opening/closing signal Igs of the power switch 102. Reference
numeral 153 is a drive transistor that is turned on when the output
of the OR circuit 152 has a logical level "H." Reference numeral
154 denotes a reverse connection protective diode that is connected
in series with the drive transistor 153. The coil 104b of the power
relay 104 is supplied with power from the vehicle battery 101 via
the reverse connection protective diode 154 and the drive
transistor 153.
[0034] Reference numeral 155 denotes the AND circuit. One input of
the AND circuit 155 is connected to the connecting point of the
output contact 104a and the reverse-blocking diode 141, and the
other input is connected to a power maintenance drive output Dy1
that is an output terminal of the microprocessor 110a. Reference
numeral 156 denotes a first input circuit that supplies the
opening/closing signal Igs of the power switch 102 to the
microprocessor 110a as a first power control signal Dx1.
[0035] Reference numeral 170 denotes an analog input interface
circuit that is provided between the analog input sensors 107 and
an analog input port An of the microprocessor 110a. The analog
input interface circuit 170 incorporates a clip diode for causing
positive or negative high-voltage noise occurring on the input
lines to go out to the power circuit and a capacitor as a noise
filter. An analog signal voltage of 0 to 5 V, for example, that is
input through the analog input port An is converted into a digital
signal by a multi-channel AD converter that is incorporated in the
microprocessor 110a.
[0036] Reference symbol 180a denotes an output interface circuit
that is provided between a digital output port Dy0 of the
microprocessor 110a and the vehicle electric loads 108a and 109a.
The output interface circuit 180a is equipped with a drive
transistor 181, a pull-up resistor 182, a logical inverter circuit
183, an inverting drive transistor 184, etc. When the digital
output port Dy0 has a logical level "H," the drive transistor 181
is turned on to supply power to the electric load 108a. When the
digital output port Dy0 has a logical level "L," the drive
transistor 184 is turned on to supply power to the electric load
109a.
[0037] Next, Operation of Embodiment 1 will be Described.
[0038] In the above-configured circuit of FIG. 1, when the power
switch 102 is closed, power is supplied from the vehicle battery
101 to the coil 104b via the reverse connection protective diode
154 and the drive transistor 153 that has been turned on by the OR
circuit 152, whereby the output contact 104a of the power relay 104
is closed.
[0039] However, if the vehicle battery 101 is set in the opposite
way in polarities, the reverse connection protective diode 154
prevents power supply to the coil 104 band hence the output contact
104a is not closed.
[0040] When the output contact 104a is closed (the vehicle battery
101 is set correctly in polarities), the constant voltage power
circuit 140 is activated via the reverse-blocking diode 141 and
generates a prescribed constant voltage Vcc, whereupon the
microprocessor 110a starts to operate.
[0041] As a result, first, a power maintenance drive signal Dy1 is
generated as a result of functioning of the power maintaining means
112a, whereby the drive transistor 153 is kept conductive via the
AND circuit 155 and the OR circuit 152. Therefore, the relaying
state of the power relay 104 is maintained even if the power switch
102 is opened afterwards.
[0042] While the power switch 102 is closed and a first power
control signal Dx1 that is supplied to the microprocessor 110a via
the first input circuit 156 has a logical level "H," the
microprocessor 110a drive-controls the various electric loads 108a
and 109a in accordance with the operation states of the various
input sensors 105 that perform on/off operations, the signal
voltage levels of the various analog input sensors 107, and the
contents of the program memory 111a.
[0043] However, when the power switch 102 is opened, the logical
level of the first power control signal Dx1 is changed from "H" to
"L." The microprocessor 110a performs save controls, for example,
saves part of learned data etc. of the RAM 114 into the nonvolatile
memory 115 and returns the operation states of the electric loads
108a and 109a to initial states, and then causes the power
maintaining means 112a to stop the output of the power maintenance
drive signal Dy1. As a result, the drive transistor 153 is turned
off and the power relay 104 is de-energized. The output voltage of
the constant voltage power circuit 140 disappears and the
microprocessor 110a stops its operation.
[0044] However, immediately before the output of the power
maintenance drive signal Dy1 is stopped, the awakening control
means 113a causes generation a timer operation start instruction
signal Dy2 and the awakening timer circuit 120 is thereby prepared
for a start of a timer operation.
[0045] Therefore, upon a lapse of a preset time of the awakening
timer circuit 120 from the stop of operation of the microprocessor
110a, the awakening timer circuit 120 generates an awakening
trigger signal Awk, whereupon a transistor 142 as a second
opening/closing element is turned on via an OR element 145 and a
drive transistor 143. As a result, power is supplied from the
vehicle battery 101 to the constant voltage power circuit 140 via
the transistor 142. The constant voltage power circuit 140
generates a prescribed constant voltage Vcc, whereby the
microprocessor 110a starts to operate.
[0046] The microprocessor 110a thus supplied with power judges that
an awakening operation state is established on the basis of the
facts that the first power control signal Dx1 has a logical level
"L" (i.e., the power switch 102 is off) and that the second power
control signal Dx2 has a logical level "H." First, the
microprocessor 110a generates a power maintenance drive signal Dy1
so that the transistor 142 will be kept conductive by the OR
element 145 even after the output of the awakening trigger signal
Awk is stopped.
[0047] Then, the microprocessor 110a stores states of
predetermined, particular input signals in the RAM 114 and judges
whether to perform an awakening operation again.
[0048] As for the necessity of continuation of the awakening
operation, the microprocessor 110a judges that the awakening
operation need not be continued if a subsequent input monitoring
operation is unnecessary when a judgment result "normal" is
produced because of no decrease in the fuel tank internal pressure
after a lapse of a sufficient time from a stop of the engine or
when a judgment result "leakage abnormality" is produced because of
an abnormal decrease in the fuel tank internal pressure.
[0049] After reading and storing the states of the particular input
signals and performing the judgment processing, the microprocessor
110a stops the output of the power maintenance drive signal Dy1.
Since the transistor 142 is turned off, the output of the constant
voltage power circuit 140 disappears and hence the microprocessor
110a stops its operation.
[0050] However, if it is necessary to perform an awakening
operation again, the microprocessor 11a generates a timer operation
start instruction signal Dy2 and thereby starts operation of the
awakening timer circuit 120 immediately before stopping the output
of the power maintenance drive signal Dy1.
[0051] Even if a power maintenance drive signal Dy1 is generated in
an awakening operation, the power relay 104 is not activated
because the output contact 104a is opened and hence the output of
the AND circuit 155 has a logical level "L."
[0052] Therefore, the various electric loads 108a and 109a are not
driven in an awakening operation and the consumption of power
supplied from the vehicle battery 101 is reduced accordingly.
[0053] In this embodiment, since the bleeder resistor 151 is
supplied with power from the connecting point of the output contact
104a and the reverse-blocking diode 141, operation states of the
input sensors 105 that perform on/off operations cannot be read at
the stage of an awakening operation.
[0054] As is understood from the above description, the power
circuit according to the first embodiment of the invention is a
power circuit of the vehicular electronic control unit 100a having
the microprocessor 110a that is supplied with power from the
vehicle battery 101 and that drives the various electric loads 108a
and 109a in accordance with the operation states of the various
input sensors 105 that generate on/off signals or the various input
sensors 107 that generate analog signals and the contents of the
program memory 111a. The vehicular electronic control unit 100a is
provided with the constant voltage power circuit 140, the awakening
timer circuit 120, and first and second power supply circuits.
[0055] The constant voltage power circuit 140 is supplied with
power from the vehicle battery 101 via the first opening/closing
element (i.e., output contact 104a; part of the first power supply
circuit) or the second opening/closing element 142 (part of the
second power supply circuit), and supplies a prescribed regulated
voltage to the microprocessor 110a, the devices accompanying the
microprocessor 110a such as the program memory 111a, the RAM 114
for computation, and the nonvolatile data memory 115, and the
input/output interface circuits 150, 170, and 180a.
[0056] The awakening timer circuit 120 is supplied with power
directly from the vehicle battery 101 and generates an awakening
trigger signal Awk upon a lapse of a prescribed time from a stop of
power supply to the microprocessor 110a. The awakening timer
circuit 120 employs power-saving-type circuit elements.
[0057] The first power supply circuit is provided with the power
relay 104 having the output contact 104a (i.e., first
opening/closing element) provided between the vehicle battery 101
and the constant voltage power circuit 140/various electric loads
108a and 109a and the coil 104b for closing the output contact
104a, and the reverse-blocking diode 141 that is connected in
series to the output contact 104a. The coil 104b is energized when
the power switch 102 is closed, that is, manipulated at a start of
driving of the vehicle. Even if the power switch 102 is opened, the
coil 104b is kept energized by a power maintenance drive signal Dy1
that is generated by the microprocessor 110a.
[0058] The second power supply circuit is provided with the second
opening/closing element 142 that at least connects the vehicle
battery 101 and the constant voltage power circuit 140. The second
opening/closing element 142 is closed when an awakening trigger
signal Awk is generated, and is kept closed by a power maintenance
drive signal Dy1 that is generated by the microprocessor 110a.
[0059] The reverse-blocking diode 141 is in such a connection
relationship as to allow power supply to the various electric loads
108a and 109a via the output contact 104a which is part of the
first power supply circuit and to prevent power supply to the
various electric loads 108a and 109a via the second opening/closing
element 142 which is part of the second power supply circuit.
[0060] Therefore, during a driving operation of the vehicular
electronic control unit 100a, the vehicular electronic control unit
100a and the vehicle electric loads 108a and 109a are supplied with
power from the single power relay 104. That is, the power circuit
is not configured so as to supply power to one of the vehicular
electronic control unit 100a and the vehicle electric loads 108a
and 109a from the power relay 104. Further, when the vehicular
electronic control unit 100a is activated in a state that the power
switch 102 is off, the vehicle electric loads 108a and 109a are not
supplied with power.
[0061] Further, the vehicular electronic control unit 100a
according to the first embodiment of the invention is housed in a
tightly closed case. The power relay 104 is provided outside the
tightly closed case whereas the second opening/closing element is
the transistor 142 that is provided inside the tightly closed
case.
[0062] Whereas the second opening/closing element 142, which is a
novel feature of the invention, is a long-life, contactless element
and is incorporated in the vehicular electronic control unit 100a,
the power relay 104 having a limited life is provided outside the
tightly closed case to facilitate its maintenance and
replacement.
[0063] Further, in the vehicular electronic control unit 10a
according to the first embodiment of the invention, first and
second power control signals Dx1 and Dx2 are input to the
microprocessor 110a and the program 112a as the power maintaining
means is stored in the program memory 111a.
[0064] The first power control signal Dx1 is an opening/closing
signal Igs of the power switch 102 and the second power control
signal Dx2 is an awakening trigger signal Awk that is generated by
the awakening timer circuit 120. When the power switch 102 is
opened, the power maintaining means 112a causes generation of a
power maintenance drive signal Dy1 for keeping the power supply
through the first power supply circuit during a first period that
is necessary for save control processing of the microprocessor
110a. While the power switch 102 is off, the power maintaining
means 112a causes generation of a power maintenance drive signal
Dy1 for keeping the power supply through the second power supply
circuit during a second period for monitoring of the states of
particular input signals.
[0065] Judging whether the current state is a delayed power shutoff
state or an awakening power supply state during a power shutoff on
the basis of the first and second power control signals Dx1 and
Dx2, the microprocessor 110a can cause the power maintaining means
112a to cause generation of a proper power maintenance drive signal
Dy1.
[0066] Still further, in the vehicular electronic control unit 100a
according to the first embodiment of the invention, the
microprocessor 110a inputs a timer operation start instruction
signal Dy2 to the awakening timer circuit 120 and the program 113a
as the awakening control means is stored in the program memory
111a. The awakening control means 113a causes the next awakening
operation by causing generation of a timer operation start
instruction signal Dy2 immediately before a stop of generation of a
power maintenance drive signal Dy1, and prohibits a subsequent
awakening operation by stopping generation of a timer operation
start instruction signal Dy2 in accordance with monitoring results
of the above-mentioned particular input signals.
[0067] If judging that an awakening operation need not be
performed, the microprocessor 110a disables operation of the second
power supply circuit, whereby the consumption of power supplied
from the vehicle battery 101 can be reduced.
[0068] Furthermore, in the vehicular electronic control unit 100a
according to the first embodiment of the invention, the power
maintenance drive signal Dy1 that is output from the microprocessor
110a to the first and second power supply circuits is output from
the common output port of the microprocessor 110a and the vehicular
electronic control unit 100a is provided with the AND circuit 155
and the OR circuit 152.
[0069] The AND circuit 155 generates a first logical signal when
the output contact 104a as the first opening/closing element is
closed and a power maintenance drive signal Dy1 is generated. The
OR circuit 152 calculates the OR of the above first logical signal
and a second logical signal that is generated when the power switch
102 is closed. The coil 104b of the power relay 104 is energized by
the resulting OR signal of the OR circuit 152.
[0070] Since the power relay 104 is not activated unless the power
switch 102 is closed even if a power maintenance drive signal Dy1
is generated, the power supply can be maintained by selectively
using the first or second power supply circuit and using a single
power maintenance drive signal Dy1.
[0071] Embodiment 2
[0072] FIG. 2 is a circuit diagram showing the configuration of the
entire power circuit of a vehicular electronic control unit
according to a second embodiment of the invention. Differences of
this power circuit from the power circuit of FIG. 1 will mainly be
described below.
[0073] In FIG. 2, reference symbol 100b denotes a vehicular
electronic control unit that is housed in a tightly closed case and
connected to the following external devices.
[0074] As in the case of FIG. 1, reference symbol 101 denotes a
vehicle battery; 102, a power switch; 104, a power relay having an
output contact 104a and a coil 104b; 105, various input sensors
that perform on/off operations; 107, various analog input sensors;
and 108b, vehicle electric loads. The various input sensors that
perform on/off operations are divided into the various input
sensors 105 of a first group and various input sensors 106 of a
second group.
[0075] The various input sensors 105 of the first group are such a
group of input sensors whose operation states need not monitored
regularly while the power switch 102 is off. On the other hand, the
various input sensors 106 of the second group are such a group of
input sensors whose operation states need to be monitored regularly
while the power switch 102 is off.
[0076] Reference numeral 103 denotes a second power relay having an
output contact 103a and a coil 103b. Reference numeral 109 denotes
an alarm/display.
[0077] As for the internal configuration of the vehicular
electronic control unit 100b, reference symbol 110b denotes a
microprocessor; 111b, a program memory such as a flash memory that
is bus-connected to the microprocessor 110b; 112b, a control
program as a power maintaining means (described later) that is
stored in the program memory 111b; 113b, a control program as an
awakening control means (described later) that is stored in the
program memory 111b; 114 and 115, a RAM and a nonvolatile data
memory (described in the first embodiment); and 116, a control
program as an alarming/displaying means that is stored in the
program memory 111b.
[0078] Reference numeral 120 denotes an awakening timer circuit
that is supplied with power directly from the vehicle battery 101.
The awakening timer circuit 120 starts a timer operation upon
instantaneously receiving a timer operation start instruction
signal Dy2 that is generated by the microprocessor 110b. Upon a
lapse of a preset, prescribed time, the awakening timer circuit 120
generates an awakening trigger signal Awk, which is supplied to an
input of an OR element 162 (described later) and is also supplied
to a second input circuit 121, which, in response, supplies a
second power control signal Dx2 to the microprocessor 110b.
[0079] Reference numeral 130 denotes a memory retention power
circuit that is supplied with power directly from the vehicle
battery 101. Reference numeral 140 denotes a constant voltage power
circuit. Supplied with power from the vehicle battery 101 via the
output contact 104a as a first opening/closing element and a
reverse-blocking diode 141, the memory retention power circuit 130
generates a constant voltage Vcc of DC 5 V, for example.
[0080] The constant voltage power circuit 140 supplies a prescribed
regulated voltage to the microprocessor 110b, the devices
accompanying the microprocessor 110b such as the program memory
111b, the RAM 114 for computation, and the nonvolatile data memory
115, input/output interface circuits 150, 160, 170, and 180b
(described later), and an abnormality storage circuit 190
(described later).
[0081] Reference numeral 150 denotes a first input interface
circuit that is provided between the first-group input sensors 105
and a digital input port Dx01 of the microprocessor 110b. Reference
numeral 151 denotes a bleeder resistor that is provided between the
connecting point of the output contact 104a and the
reverse-blocking diode 141 and the first-group input sensors 105.
The first input interface circuit 150 level-converts DC 12 V as an
input signal voltage into DC 5 V and incorporates a capacitor as a
noise filter.
[0082] Reference numeral 152 denotes an OR circuit that receives,
as inputs, a power maintenance drive signal Dyl1 and an
opening/closing signal Igs of the power switch 102. Reference
numeral 153 is a drive transistor that is turned on when the output
of the OR circuit 152 has a logical level "H." Reference numeral
154 denotes a reverse connection protective diode that is in series
with the drive transistor 153. The coil 104b of the power relay 104
is supplied with power from the vehicle battery 101 via the reverse
connection protective diode 154 and the drive transistor 153.
[0083] Reference numeral 156 denotes a first input circuit that
supplies the opening/closing signal Igs of the power switch 102 to
the microprocessor 110b as a first power control signal Dx1.
Reference numeral 157 denotes a third input circuit that supplies
an opening/closing signal of the output contact 104a to the
microprocessor 110b as a third power control signal Dx3.
[0084] Reference numeral 160 denotes a second input interface
circuit that is provided between the second-group input sensors 106
and a digital input port DxO2 of the microprocessor 110b. Reference
numeral 161 denotes a bleeder resistor that is provided between the
connecting point of the reverse-blocking diode 141 and the constant
voltage power circuit 140 and the first-group input sensors 106.
The second input interface circuit 160 level-converts DC 12 V as an
input signal voltage into DC 5 V and incorporates a capacitor as a
noise filter.
[0085] Reference numeral 162 denotes an OR element that receives,
as inputs, a power maintenance drive signal Dyl2 and the
above-mentioned awakening trigger signal Awk. Reference numeral 163
is a drive transistor that is turned on when the output of the OR
element 162 has a logical level "H." Reference numeral 164 denotes
a reverse connection protective diode that is in series with the
drive transistor 163. The coil 103b of the power relay 103 is
supplied with power from the vehicle battery 101 via the reverse
connection protective diode 164 and the drive transistor 163.
[0086] The output contact 103a as a second opening/closing element
is provided between the vehicle battery 101 and the constant
voltage power circuit 140. The reverse-blocking diode 141 exists in
the circuit from the output contact 103a to the vehicle electric
loads 108b and the alarm/display 109 to prevent power supply along
this circuit.
[0087] Reference numeral 170 denotes an analog input interface
circuit that is provided between the analog input sensors 107 and
an analog input port An of the microprocessor 110b. Reference
symbol 180b denotes an output interface circuit that is provided
between a digital output port Dy0 of the microprocessor 110b and
the vehicle electric loads 108b. Reference numeral 190 denotes an
abnormality storage circuit that is a flip-flop circuit. The set
input S of the abnormality storage circuit 190 is connected to an
abnormality alarm display signal Dy3 of the microprocessor 110b,
and its reset input R is connected to are set pulse generation
circuit (not shown) that generates a pulse signal PLs when the
power switch 102 is turned from off to on. The alarm/display 109
operates when an abnormality has been stored in the abnormality
storage circuit 190.
[0088] Operation of Embodiment 2 will be Described.
[0089] In the above-configured circuit of FIG. 2, when the power
switch 102 is closed, power is supplied from the vehicle battery
101 to the coil 104b via the reverse connection protective diode
154 and the drive transistor 153 that has been turned on by the OR
circuit 152, whereby the output contact 104a of the power relay 104
is closed.
[0090] However, if the vehicle battery 101 is set in the opposite
way in polarities, the reverse connection protective diode 154
prevents energization of the coil 104b and hence the output contact
104a is not closed.
[0091] When the output contact 104a is closed (the vehicle battery
101 is set correctly in polarities), the constant voltage power
circuit 140 is activated via the reverse-blocking diode 141 and
generates a prescribed constant voltage Vcc, whereupon the
microprocessor 110b starts to operate.
[0092] As a result, first, a power maintenance drive signal Dyl1 is
generated as a result of functioning of the power maintaining means
112b, whereby the drive transistor 153 is kept conductive via the
OR circuit 152. Therefore; the relaying state of the power relay
104 is maintained even if the power switch 102 is opened
afterwards.
[0093] While the power switch 102 is closed and a first power
control signal Dx1 that is supplied to the microprocessor 110b via
the first input circuit 156 has a logical level "H," the
microprocessor 110b drive-controls the various electric loads 108b
in accordance with the operation states of the first and second
input sensors 105 and 106, the signal voltage levels of the various
analog input sensors 107, and the contents of the program memory
111b.
[0094] However, when the power switch 102 is opened, the logical
level of the first power control signal Dx1 is changed from "H" to
"L." The microprocessor 110b performs save controls, for example,
saves part of learned data etc. of the RAM 114 into the nonvolatile
memory 115 and returns the operation states of the electric loads
108b to initial states, and then causes the power maintaining means
112b to stop the output of the power maintenance drive signal
Dyl1.
[0095] As a result, the drive transistor 153 is turned off and the
power relay 104 is de-energized. The output voltage of the constant
voltage power circuit 140 disappears and the microprocessor 110b
stops its operation.
[0096] However, immediately before the output of the power
maintenance drive signal Dyl1 is stopped, the awakening control
means 113b causes generation of a timer operation start instruction
signal Dy2 and the awakening timer circuit 120 is thereby prepared
for a start of a timer operation.
[0097] Therefore, upon a lapse of a preset time of the awakening
timer circuit 120 from the stop of operation of the microprocessor
110b, the awakening timer circuit 120 generates an awakening
trigger signal Awk, whereupon the coil 103b of the second power
relay 103 is supplied with power via the drive transistor 163 that
has been turned on by the OR element 162 and the output contact
103a as the second opening/closing element is turned on.
[0098] As a result, power is supplied from the vehicle battery 101
to the constant voltage power circuit 140 via the output contact
103a. The constant voltage power circuit 140 generates a prescribed
constant voltage Vcc, whereby the microprocessor 110b starts to
operate.
[0099] The microprocessor 110b thus supplied with power judges that
an awakening operation state is established on the basis of the
facts that the first power control signal Dx1 has a logical level
"L" (i.e., the power switch 102 is off) and that the second power
control signal Dx2 has a logical level "H." First, the
microprocessor 110b generates a power maintenance drive signal Dyl2
so that the second power relay 103 will be kept activated by the OR
element 162 and the drive transistor 163 even after the output of
the awakening trigger signal Awk is stopped.
[0100] Then, the microprocessor 110b stores states of
predetermined, particular input signals in the RAM 114 and judges
whether to perform an awakening operation again.
[0101] After reading and storing the states of the particular input
signals and performing the judgment processing, the microprocessor
110b stops the output of the power maintenance drive signal Dyl2.
Since the drive transistor 163 is turned off, the output of the
constant voltage power circuit 140 disappears and hence the
microprocessor 110b stops its operation.
[0102] However, if it is necessary to perform an awakening
operation again, the microprocessor 110b generates a timer
operation start instruction signal Dy2 and thereby starts operation
of the awakening timer circuit 120 immediately before stopping the
output of the power maintenance drive signal Dyl2.
[0103] In this embodiment, since the bleeder resistor 161 is
located at such a position as to be supplied with power from the
output contact 103a, operation states of the second group input
sensors 106 can be read at the stage of an awakening operation.
[0104] In contrast, as for the first-group input sensors 105 that
need not be monitored during an awakening operation, the
reverse-blocking diode 141 prevent power supply to the bleeder
resistor 151.
[0105] On the other hand, when the power switch 102 has been
opened, the logical level of the first power control input signal
Dx1 has been changed to "L," and the output of the power
maintenance drive signal Dyl1 has stopped, the power relay 104
should be de-energized and the output contact 104a should be
opened. However, if the output contact 104a is kept conductive
because of welding, the power supply to the constant voltage power
circuit 140 is maintained and the third power control signal Dx3
having a logical level "H" is kept input to the microprocessor 110b
via the third input circuit 157.
[0106] In response to the occurrence of this abnormal state, the
microprocessor 110b cooperates with the alarming/displaying means
116 to generate an abnormality alarm display signal Dy3 and thereby
causes operation of the alarm/display 109 via the abnormality
storage circuit 190.
[0107] (3) Features of Configuration and Advantages of Embodiment
2
[0108] As is understood from the above description, the power
circuit according to the second embodiment of the invention is a
power circuit of the vehicular electronic control unit 100b having
the microprocessor 110b that is supplied with power from the
vehicle battery 101 and that drives the various electric loads 108b
in accordance with the operation states of the first and second
input sensors 105 and 106 that generate on/off signals or the
various input sensors 107 that generate analog signals and the
contents of the program memory 111b. The vehicular electronic
control unit 100b is provided with the constant voltage power
circuit 140, the awakening timer circuit 120, and first and second
power supply circuits.
[0109] The constant voltage power circuit 140 is supplied with
power from the vehicle battery 101 via the first opening/closing
element (i.e., output contact 104a; part of the first power supply
circuit) or the second opening/closing element (i.e., output
contact 103a; part of the second power supply circuit), and
supplies a prescribed regulated voltage to the microprocessor 110b,
the devices accompanying the microprocessor 110b such as the
program memory 111b, the RAM 114 for computation, and the
nonvolatile data memory 115, the input/output interface circuits
150, 160, 170, and 180b, and the abnormality storage circuit
190.
[0110] The awakening timer circuit 120 is supplied with power
directly from the vehicle battery 101 and generates an awakening
trigger signal Awk upon a lapse of a prescribed time from a stop of
power supply to the microprocessor 110b. The awakening timer
circuit 120 employs power-saving-type circuit elements.
[0111] The first power supply circuit is provided with the power
relay 104 having the output contact 104a (i.e., first
opening/closing element) provided between the vehicle battery 101
and the constant voltage power circuit 140/various electric loads
108b and the coil 104b for closing the output contact 104a, and the
reverse-blocking diode 141 that is connected in series to the
output contact 104a. The coil 104b is energized when the power
switch 102 is closed, that is, manipulated at a start of driving of
the vehicle. Even if the power switch 102 is opened, the coil 104b
is kept energized by a power maintenance drive signal Dyl1 that is
generated by the microprocessor 10b.
[0112] The second power supply circuit is provided with the second
power relay 103 having the output contact 103a (i.e., second
opening/closing element) that at least connects the vehicle battery
101 and the constant voltage power circuit 140 and the coil 103b
for closing the output contact 103a. The coil 103a is energized
when an awakening trigger signal Awk is generated, and is kept
energized by a power maintenance drive signal Dyl2 that is
generated by the microprocessor 110b.
[0113] The reverse-blocking diode 141 is in such a connection
relationship as to allow power supply to the various electric loads
108b via the output contact 104a which is part of the first power
supply circuit and to prevent power supply to the various electric
loads 108b via the output contact 103a which is part of the second
power supply circuit.
[0114] Therefore, during a driving operation of the vehicular
electronic control unit 110b, the vehicular electronic control unit
100b and the vehicle electric loads 108b are supplied with power
from the single power relay 104. That is, the power circuit is not
configured so as to supply power to one of the vehicular electronic
control unit 100b and the vehicle electric loads 108b from the
power relay 104. Further, when the vehicular electronic control
unit 100b is activated in a state that the power switch 102 is off,
the vehicle electric loads 108b are not supplied with power.
[0115] Further, since the second power relay 103 is used as the
second opening/closing element, the degree of power generation is
lower than in the case of using a transistor and the leakage
current during opening of the output contact 103a is small.
[0116] Further, in the vehicular electronic control unit 100b
according to the second embodiment of the invention, first and
second power control signals Dx1 and Dx2 are input to the
microprocessor 110b and the program 112b as the power maintaining
means is stored in the program memory 111b.
[0117] The first power control signal Dx1 is an opening/closing
signal Igs of the power switch 102 and the second power control
signal Dx2 is an awakening trigger signal Awk that is generated by
the awakening timer circuit 120. When the power switch 102 is
opened, the power maintaining means 112b causes generation of a
power maintenance drive signal Dy11 for keeping the power supply
through the first power supply circuit during a first period that
is necessary for save control processing of the microprocessor
110b. While the power switch 102 is off, the power maintaining
means 112b causes generation of a power maintenance drive signal
Dyl2 for keeping the power supply through the second power supply
circuit during a second period for monitoring of the states of
particular input signals.
[0118] Judging whether the current state is a delayed power shutoff
state or an awakening power supply state during a power shutoff on
the basis of the first and second power control signals Dx1 and
Dx2, the microprocessor 110b can cause the power maintaining means
112b to cause generation of a proper power maintenance drive signal
Dy11 or Dy12.
[0119] Still further, in the vehicular electronic control unit 100b
according to the second embodiment of the invention, the
microprocessor 110b inputs a timer operation start instruction
signal Dy2 to the awakening timer circuit 120 and the program 113b
as the awakening control means is stored in the program memory
111b.
[0120] The awakening control means 113b causes the next awakening
operation by causing generation of a timer operation start
instruction signal Dy2 immediately before a stop of generation of a
power maintenance drive signal Dyl1 or Dyl2, and prohibits a
subsequent awakening operation by stopping generation of a timer
operation start instruction signal Dy2 in accordance with
monitoring results of the above-mentioned particular input
signals.
[0121] If judging that an awakening operation need not be
performed, the microprocessor 110b disables operation of the second
power supply circuit, whereby the consumption of power supplied
from the vehicle battery 101 can be reduced.
[0122] Further, in the vehicular electronic control unit 100b
according to the second embodiment of the invention, the various
input sensors 105 and 106 are separately connected to the
microprocessor 10b via the first and second input interface
circuits 150 and 160.
[0123] The first-group input sensors 105 that are connected to the
first input interface circuit 150 are also connected to the first
power supply circuit. The first-group input sensors 105 are a group
of sensors that need not be monitored while the power switch 102 is
off.
[0124] The second-group input sensors 106 that are connected to the
second input interface circuit 160 are also connected to the second
power supply circuit. The second-group input sensors 106 are a
group of sensors that need to be monitored while the power switch
102 is off or a group of sensors whose current consumption is very
small though they need not be monitored while the power switch 102
is off.
[0125] With this measure, the consumption of power supplied from
the vehicle battery 101 during the awakening operation for input
monitoring can be reduced.
[0126] Furthermore, in the vehicular electronic control unit 100b
according to the second embodiment of the invention, the program
memory 111b contains the program 116 as the alarming/displaying
means. The alarming/displaying means 116 causes the abnormality
storage circuit 190 to operate and thereby announces occurrence of
an abnormality using the alarm/display 109 if the output contact
104a of the power relay 104 is closed in a state that the power
switch 102 is off and a power maintenance drive signal Dy11 is not
generated.
[0127] Therefore, if an welding abnormality has occurred in the
output contact 104a, the alarm/display 109 is activated and the
occurrence of the abnormality is thereby announced with only a
short delay from, that is, immediately after, turning-off of the
power switch 102 by the driver. An abnormal discharge of the
vehicle battery 101, resulting burning damage, or a like accident
can be prevented.
* * * * *